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A novel underwater bipedal walking soft robot bio-inspired by the coconut octopus
Abstract
In order to increase the compatibility between underwater robots and the underwater environment and inspired by the coconut octopus's underwater bipedal walking, a method was proposed for bipedal walking for an underwater soft robot based on a spring-loaded inverted pendulum model. Using the characteristics of octopus tentacles rolling on the ground, a wrist arm was designed using the cable-driven method, and an underwater spring-loaded inverted pendulum bipedal walking model was established, which makes an underwater soft robot more suitable for moving on uneven ground. An underwater bipedal walking soft robot based on coconut octopus was then designed, and a machine vision algorithm was used to extract the motion information for analysis. Experimental analysis shows that the underwater bipedal walking robot can achieve an average speed of 6.48 cm⁄s, and the maximum instantaneous speed can reach 8.14 cm⁄s.
... After millions of years of evolution, organisms usually have good motility, flexibility, and environmental adaptability, which have inspired the design of robots. In recent decades, researchers have developed many soft robots inspired by natural organisms or their organs, such as earthworms [1], caterpillars [2], octopuses [3], fishes [4], and starfishes [5]. A "dancer" in the ocean, jellyfish have a soft body, low noise and energy consumption, high swimming efficiency, and simple anatomical structures. ...
... The weight of the prototype is 512 g, and the density is 1.031 g/cm 3 . Under the relaxation state (as shown in Figure 2b), the diameter is nearly 210 mm with a height of 80 mm. ...
... By loading voltage to the SMA artificial muscle, SMA wires generate heat to undergo a phase change, which generates force and displacement output. The contraction process of SMA wires is thus transformed into the bending motion of the artificial The weight of the prototype is 512 g, and the density is 1.031 g/cm 3 . Under the relaxation state (as shown in Figure 2b), the diameter is nearly 210 mm with a height of 80 mm. ...
This paper presented a flexible and easily fabricated untethered underwater robot inspired by Aurelia, which is named “Au-robot”. The Au-robot is actuated by six radial fins made of shape memory alloy (SMA) artificial muscle modules, which can realize pulse jet propulsion motion. The thrust model of the Au-robot’s underwater motion is developed and analyzed. To achieve a multimodal and smooth swimming transition for the Au-robot, a control method integrating a central pattern generator (CPG) and an adaptive regulation (AR) heating strategy is provided. The experimental results demonstrate that the Au-robot, with good bionic properties in structure and movement mode, can achieve a smooth transition from low-frequency swimming to high-frequency swimming with an average maximum instantaneous velocity of 12.61 cm/s. It shows that a robot designed and fabricated with artificial muscle can imitate biological structures and movement traits more realistically and has better motor performance.
... Thus, where a traditional robot may require fewer than 10 sensors to determine pose and interaction, a soft robot could easily require over a hundred. Several groups have tried machine vision methods to alleviate the rapidly growing burden of so many sensors, using cameras and motion capture to directly measure soft robot pose [3][4][5]. While this is effective in some applications, and the work is quite compelling, this technique is ill-suited to applications with a likelihood of obstructed views (such as reaching into boxes to retrieve objects in order fulfillment or laparoscopic surgery). ...
... The elastomeric construct is removed from Mold 1, the two bars for the microfluidic pressure sensor are removed, a short piece of silicone tubing is inserted, connecting the two microfluidic channels, and an end-cap (shown in green) is secured to the distal end of the elastomer ( Figure A2B). The construct is installed into another mold (Mold 2) and instrumented with eight more bars which will contain the other eight fibers (1)(2)(3)(4)(6)(7)(8)(9). Microfluidic channels are instrumented with temporary PTFE tubing to prevent elastomer ingress. ...
... verifies this. Solid lines (fiber1,4,8) are positive, dotted lines (fibers 2,6,9) are negative, and dashed lines (fiber 3, 5, 7) moved little at all. Due to the test setup (distal end of finger pulled upward and allowed to move laterally) some tension in the finger caused the midplane to stretch slightly, causing slight negative values in dashed lines. ...
Current challenges in soft robotics include sensing and state awareness. Modern soft robotic systems require many more sensors than traditional robots to estimate pose and contact forces. Existing soft sensors include resistive, conductive, optical, and capacitive sensing, with each sensor requiring electronic circuitry and connection to a dedicated line to a data acquisition system, creating a rapidly increasing burden as the number of sensors increases. We demonstrate a network of fiber-based displacement sensors to measure robot state (bend, twist, elongation) and two microfluidic pressure sensors to measure overall and local pressures. These passive sensors transmit information from a soft robot to a nearby display assembly, where a digital camera records displacement and pressure data. We present a configuration in which one camera tracks 11 sensors consisting of nine fiber-based displacement sensors and two microfluidic pressure sensors, eliminating the need for an array of electronic sensors throughout the robot. Finally, we present a Cephalopod-chromatophore-inspired color cell pressure sensor. While these techniques can be used in a variety of soft robot devices, we present fiber and fluid sensing on an elastomeric finger. These techniques are widely suitable for state estimation in the soft robotics field and will allow future progress toward robust, low-cost, real-time control of soft robots. This increased state awareness is necessary for robots to interact with humans, potentially the greatest benefit of the emerging soft robotics field.
... Given that the density-based solver is typically reserved for high Mach number scenarios, it is not applicable to the model in this paper. Therefore, the default pressure-based solver in Fluent is adopted for the simulation and the remaining conditions, such as the residual convergence of 10 5 − , the turbulent kinetic energy, the continuity requirements, the energy, and other convergence conditions are set to 10 3 − . Once the computational model and boundary condition treatments are established, attention shifts to setting the solution parameters. ...
... Given that the density-based solver is typically reserved for high Mach number scenarios, it is not applicable to the model in this paper. Therefore, the default pressure-based solver in Fluent is adopted for the simulation and the remaining conditions, such as the residual convergence of 10 5 − , the turbulent kinetic energy, the continuity requirements, the energy, and other convergence conditions are set to 10 3 − . Once the computational model and boundary condition treatments are established, attention shifts to setting the solution parameters. ...
In marine engineering and water conservancy projects, dredging often occurs due to silt accumulation, which can impede the long-term development of water ecosystems and water storage systems. To enhance dredging efficiency and the performance of dredging machines, a novel type of winch suction underwater dredging robot was designed. Computational fluid dynamics software was utilized to establish a fluid model of the robot’s winch suction dredging device and conduct model simulation experiments. The simulation test results were used to investigate the factors influencing dredging performance and their impact laws. Five key factors—namely, the reamer rotational speed, reamer arrangement angle, water flow rate, inlet pipe diameter, and outlet pipe diameter—were selected for consideration. By setting up various sets of factor levels, the significant influence of different factors on dredging efficiency was examined. Analysis of variance was employed to analyse the results of the orthogonal experimental design, leading to the identification of optimal factor levels and the establishment of an optimal scheme group. The results of the optimal scheme were verified, demonstrating a 13.049% increase in dredging efficiency and a 19.23% decrease in power consumption of the sludge pump compared to the initial experimental setup. The performance of the optimal program surpassed that of all the experimental designs and met the design requirements.
... The arm was equipped with a cable-driven soft gripper, enabling it to perform various picking operations ( Figure 2.11a). Continuum soft robots also use tendon actuation, like the tentacle in [45], [46] (Figure 2.12). ...
... 12: Stretch motion of cable-driven bionic tentacles[46]. ...
... A bipedal walking of a soft robot inspired by a coconut octopus has been studied. The gait analysis of the bipedal octopus is presented along with the design of the mechanical structure and the control systems [33]. ...
... walking of a soft robot inspired by a coconut octopus has been studied. The gait analysis of the bipedal octopus is presented along with the design of the mechanical structure and the control systems [33]. In this paper, a simplistic version of a biomimetic soft robotic octopus tentacle using coiled Shape Memory Alloys embedded in Ecoflex silicone is presented. ...
Traditional rigid grippers that are used for underwater systems lack flexibility and have lower degrees of freedom. These systems might damage the underwater environment while conducting data acquisition and data sampling. Soft robotics, which is mainly focused on creating robots with extremely soft materials are more delicate for the grasping of objects underwater. These systems tend to damage the underwater ecosystem in the least possible way. In this paper, we have presented a simplified design of a soft arm inspired by the octopus arm actuated by coiled Shape Memory Alloys (SMAs) using completely flexible lightweight material. The characterization arm performance under various load and input current conditions is shown. We hope this work will serve as a basis for the future of underwater grasping utilizing soft robotics.
... Although wheeled robots have been used in various engineering applications due to easy and simple steering operation, they face challenges on rugged and uneven terrains [1]. Legged terrestrial mobile robots are more versatile in the locomotory performance, and recently various bioinspired legged robots from animals and insects have been studied and developed in the form of two-legged (bipedal) [2,3], four-legged (quadrupedal) [4,5], sixlegged (hexapedal) [6,7], and eight-legged (octopedal) [8,9] robots. It has been investigated that more legs on a robot yield superior stability to less legs on a robot during locomotion. ...
... During the operation of the system, as error changed (to 0), the positions of the dynamic poles finally moved to −1, −1.93, −13.46, and −16.11 on the g-plane. The zeros located at around −1 and −2 by the compensator attracted two poles (g 1,2 ) not to affect the dominant poles (g 3,4 ). The controlled system response initially exhibited the trajectory of an underdamped system with a small damping ratio (ζ(t) = 0.35) and a large bandwidth (ω BW (t) = 35.62 ...
Hybrid soft leg systems have been studied for advanced gaits of soft robots. However, it is challenging to analyze and control hybrid soft legs due to their nonlinearity. In this study, we adopted dynamic pole motion (DPM) to analyze stability of a nonlinear hybrid soft leg system with dynamic Routh’s stability criterion and to design a proper controller for the nonlinear system with an error-based adaptive controller (E-BAC). A typical hybrid soft leg system was taken as an example, as such a system can easily become unstable and needs a controller to get the system back to a stable state. Specifically, E-BAC was designed to control the unstable hybrid soft leg fast with a minimal overshoot. As a nonlinear controller, the implanted E-BAC in a feedback control system includes two dominant dynamic parameters: the dynamic position feedback Kpe,t and the dynamic velocity feedback Kve,t. These parameters were properly selected, and the feedback was continuously varying as a function of system error et, exhibiting an adaptive control behavior. The simulation shows that this approach for constructing an adaptive controller can yield a very fast response with no overshoot.
... crawling locomotion) and faster gaits (bipedal and hopping) have been characterized, and the adopted locomotory solutions were exploited to increase the mobility of underwater robots in the benthic realm (Calisti et al., 2014;Calisti, 2017;Wu et al., 2022). Furthermore, biorobotics research has been inspired also by the coconut octopus's underwater multipedal walking, considering octopus arms rolling on the ground to enable a walking soft robot model more suitable for moving on uneven surfaces (Wu et al., 2021). ...
This chapter describes past and present publication trends in octopus research following a systematic mapping approach. Publication rates in popular research topics such as life history and ecology are decreasing, while others are increasing and taking the spotlight. Interest in behaviour has seen a considerable uptick in recent years. Also, rapid advances, emerging tools, and widespread access to DNA sequence information have stimulated an increased focus on topics relating to genomics & evolution. Research related to diversity & bBiogeo-graphy is also increasing, especially in the context of the concurrent biodiversity and climate crises. Although global change represents the least studied topic to date, interest has increased tremendously over the past 5 years, with more than double the publication rate observed for behaviour (the topic with the second largest publication rate). Our analysis also provides a geographical perspective; the food and argriculture organization region with the most octopus-related studies is the Mediterranean, followed by the Northeast and Western-Central Atlantic Ocean. Regarding species of interest, Octopus vulgaris stands out as the overwhelming front-runner Octopus Biology and Ecology. https://doi. 421 representing more than half of all records and over five times more than the second most studied species, Octopus maya. We also provide a discussion on future directions for key subjects, including behaviour and cognition, iEcology and citizen science, bio-robotics, deep-sea research, climate change, and culture and welfare, among others, with the hope of providing an agenda for future research.
... Thus, where a traditional robot may require fewer than 10 sensors to determine pose and interaction, a soft robot could easily require over a hundred. Several groups have tried machine vision methods to alleviate the rapidly growing burden of so many sensors, using cameras and motion capture to directly measure soft robot pose [33], [89], [90]. While this is effective in some applications, and the work is quite compelling, this technique is ill-suited to applications with a likelihood of obstructed views (such as reaching into boxes to retrieve objects in order fulfillment or laparoscopic surgery). ...
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Soft robots are a new field in robotics that shows an increasing potential to dramatically expand the capabilities of robots. We have analyzed the advantages and disadvantages of traditional rigid robots and soft robots, as well as the timing and occasions for their application. The characteristics of these two types of robots are completely different. However, in real human life, we are faced with a situation that falls between the characteristics of these two types of robots. Sometimes we need to grasp fragile objects, sometimes we need to lift heavy objects, and sometimes we need to press buttons or electrical switches and other daily actions. We need to think more formally about whether soft robots can perform these tasks and what critical areas are still lacking that need to be addressed. Thus, their underlying subsystems (actuation, sensing, control) and their role in robotics must be reconsidered. We first rethink sensing, in which traditional rigid robot sensing is very intuitive, using as many sensors as their degrees of freedom to describe the state of the robot. However, for soft robots, sensing becomes very difficult. Secondly, we rethink actuation; soft actuators are great for applying a distributed force on fragile objects. But the backdrivability that gives them the advantage also limits their ability to generate high forces.In this dissertation, we rethought the soft systems and proposed the fundamental novel types of soft sensor and actuator necessary to develop the field of soft robotics from interesting concepts to useful devices. We demonstrate a network of fiber-based displacement sensors to measure robot state (bend, twist, elongation) and two microfluidic pressure sensors to measure overall and local pressures. The fiber-based sensors are fundamentally designed to be used in groups and leverage the concepts from beam theory and mechanics of materials to infer system state from a strategically located system of sensors. Intended to be built into a soft robot at the system level, a properly configured array of these deformation and pressure sensors can give state awareness far beyond that of individual sensors. We present a bioinspired soft finger with a soft-rigid hybrid structure that can have multiple curves and force direction controllability to provide force in a specific direction. The soft and rigid states of multiple independent locking modules can be controlled independently by connecting them into a chain-like system. We have performed a modeling analysis of this controlled soft-rigid module, which provides an adaptable and scalable design framework for future bioinspired robotic fingers. We propose a new soft-rigid hybrid structure design and a method of interaction between pneumatic and tendon-driven actuators. The two actuation methods can increase the finger’s flexibility, allowing it to grasp objects of various shapes, sizes, and weights quickly and stably while providing sufficient force in specific directions. We have also added a nail mechanism to the tip of the finger, which helps the finger grip flat or small objects. Lastly, we studied the possible power source of soft robots and found that if we look at the energy density alone, chemical reactions can provide a higher energy source than those energy sources with rigid components such as lithium batteries, compressed air, liquid carbon dioxide, etc. However, the challenge of chemical reactions is to control the fluid efficiently. We develop a normally open passive microfluidic valve with reduced-order control for a micro-combustion chamber. This passive microfluidic valve can be installed on a micro-combustion chamber and is responsible for all fluid control, including intake and exhaust. This novel passive microfluidic valve may also be used in other applications, such as sensors for soft robotics.
... Underwater Spring-Loaded Inverted Pendulum (USLIP) for underwater-legged locomotion [25,26]. Like the running model in the SLIP model, this gait is also divided into two phases: (a) the stance phase-the leg contacts the ground and actively elongates. ...
In developing and exploring extreme and harsh underwater environments, underwater robots can effectively replace humans to complete tasks. To meet the requirements of underwater flexible motion and comprehensive subsea operation, a novel octopus-inspired robot with eight soft limbs was designed and developed. This robot possesses the capabilities of underwater bipedal walking, multi-arm swimming, and grasping objects. To closely interact with the underwater seabed environment and minimize disturbance, the robot employs a cable-driven flexible arm for its walking in underwater floor through a bipedal walking mode. The multi-arm swimming offers a means of three-dimensional spatial movement, allowing the robot to swiftly explore and navigate over large areas, thereby enhancing its flexibility. Furthermore, the robot’s walking arm enables it to grasp and transport objects underwater, thereby enhancing its practicality in underwater environments. A simplified motion models and gait generation strategies were proposed for two modes of robot locomotion: swimming and walking, inspired by the movement characteristics of octopus-inspired multi-arm swimming and bipedal walking. Through experimental verification, the robot’s average speed of underwater bipedal walking reaches 7.26 cm/s, while the horizontal movement speed for multi-arm swimming is 8.6 cm/s.
... Since the development of "RoboTuna" by Triantafyllou and Triantafyllou [36], significant advancements have been made in the design, fabrication, and control of bioinspired aquatic robotics. These achievements have involved the emulation of various aquatic organisms, including fish [2], frogs [46,47], octopuses [48][49][50], and jellyfish [51,52]. By combining principles from mechanics, fluid dynamics, and biology, the performance of bionic robots continues to improve steadily. ...
With the continuous deepening of ocean exploration, submersibles have become essential tools that have garnered considerable attention in the academia. As of the 2020s, driven by advancements in materials and various disciplines, the development of submersibles has undergone important transformations compared to their initial state. In this paper, we provide a comprehensive review of the developments in submersible technology from a historical point of view. In particular, we emphasize the emergence of the robotic fish-type submersibles. This process is characterized by the fusion of biomimicry and advanced technologies, and represents the future direction of submersible developments. Thus, we also emphasize the key technological challenges that robotic fish-type submersibles should focus on. Finally, we outline a general procedure for developing biomimetic robotic fish-type submersibles by drawing insights from a recent 2,000-m biomimicry prototype study. We hope to pave a smoother path for the future advancement of submersibles.
... Inspiration from the diverse creatures in nature has sparked the emergence of numerous soft robots in recent years. These robots, such as soft robotic octopuses, snakes, caterpillars, birds and click beetles [1][2][3][4][5], exhibit remarkable flexibility in locomotion, exceptional dexterity in manipulation, and advanced adaptability to complicated environments. In contrast to conventional piece-wise rigid machines, soft robots possess an infinite number of Degrees of Freedom (DOFs) and inherent softness, which enables them to overcome the limitations of confined space, offers enhanced dexterity, and ensures safer interactions with humans. ...
Purpose of review
In this review, we briefly summarize the numerical methods commonly used for the nonlinear dynamic analysis of soft robotic systems. The underlying mechanical principles as well as the geometrical treatment tailored for soft robots are introduced with particular emphasis on one-dimensional models. Additionally, the review encompasses three-dimensional frameworks, available simulation packages, and various types of interaction models, shedding light on the design, actuation, motion control, and internal and external forces of soft robots.
Recent findings
Reduced-order models can offer high efficiency in characterizing nonlinear deformations, allowing convenient tailoring based on specific structural and material configurations. For pursuing high simulation accuracy and detailed mechanics, the finite element method proves to be a valuable tool through numerous off-the-shelf platforms. Furthermore, machine learning has emerged as a promising tool to effectively address the challenges within the mechanics community.
Summary
A wide range of kinematic and dynamic numerical models is available for simulating the behaviors of soft robots, offering exceptional adaptability to different geometries and structures based on existing modeling theories and numerical solution algorithms. However, the trade-off between computational complexity and simulation accuracy remains a challenge in achieving fast, accurate, and robust control of soft robots in complex environments.
... Marine creatures have evolved multiple gait and motion techniques along with flexible structures, that allow them to move in different and efficient ways (Gemmell et al., 2015;Mo et al., 2020;Wereley, 2021). These techniques have been widely studied and have served as inspiration for different kinds of underwater mobile soft robots like swimmers (Patterson et al., 2020;Ulloa et al., 2020;Shen et al., 2020;Huang et al. (2022;2021), walkers (Corucci et al., 2015;Wu et al., 2021), crawlers or a combination of these gaits like swimming and crawling (Arienti et al., 2013;Giorgio-Serchi et al., 2017). Inspired by the sea star locomotion ( Figure 1A) which includes crawling and grounded bouncing (Heydari et al., 2020), many attempts have been made to create a sea star crawler (Youssef et al., 2022). ...
Over the years, efforts in bioinspired soft robotics have led to mobile systems that emulate features of natural animal locomotion. This includes combining mechanisms from multiple organisms to further improve movement. In this work, we seek to improve locomotion in soft, amphibious robots by combining two independent mechanisms: sea star locomotion gait and gecko adhesion. Specifically, we present a sea star-inspired robot with a gecko-inspired adhesive surface that is able to crawl on a variety of surfaces. It is composed of soft and stretchable elastomer and has five limbs that are powered with pneumatic actuation. The gecko-inspired adhesion provides additional grip on wet and dry surfaces, thus enabling the robot to climb on 25° slopes and hold on statically to 51° slopes.
... Among others, soft robots have emerged rapidly in recent years, which can break through the limitations of traditional rigid robots in certain application scenarios such as human-robot interaction and rugged environments [6,7]. Besides these, soft robots have unparalleled advantages in biomedical applications such as surgery [8], directional drug delivery [9][10][11], dredging of blood vessels [12], targeted examination [13], under-water explorations [14] with the advantage of great flexibility. Up to now, a variety of soft robots have been designed to meet different engineering needs. ...
Magnetic field driven robots have a wide spectrum of applications in many areas, such as in biomedical experiment, surgical tools, aerospace and mechanical engineering. In the present study, we make a comprehensive investigation on the deformation and motion of a mesh shaped robot controlled by the magnet. First we have prepared the matrix material of the robot, which is a mixture of silica gel and NdFeB powders. Then the deformation and motion of the robot driven by the magnet are recorded, and the warping and arching configurations are analyzed. The experimental phenomena have been compared with the numerical simulation and theoretical analysis, and the results are in excellent agreement. These findings are beneficial to engineer new types of intelligent robots, as well as to put them in various industrial settings.
... Soft miniature robots [1], ranging from nanometres to millimetres, have attracted considerable attention in recent years due to the rapid advances in material fabrication and mechanical manufacture technologies [2,3]. Soft robots have an unmatched advantage to adapt various unstructured environments with respect to their rigid counterparts, demonstrating unprecedented unique applications prospects [4][5][6], such as precise surgery [7], targeted examination [8], under-water explorations [9] and drug delivery [10]. Moreover, soft robots can exhibit safe interaction performances with human body and great flexibility to respond because of their high compliance and adaptability [11]. ...
The compression packer is an important downhole oil production tool, and its failure is mainly attributed to the degradation of its embedded rubber cylinders under the action of high temperatures. In the present study we have made a comprehensive investigation on the mechanical response of the sealing packer based on two rubber materials at high temperatures. Firstly, by measuring the material parameters under different temperatures, we established the constitutive relationships of the two rubber materials (Aflas and Kalrez) in consideration of the temperature effect, in the light of the Mooney-Rivlin model. Next, the sealing performances of two optimized packers were analyzed including Aflas and Kalrez rubber cylinders. The effects of high temperature and the initial setting pressure on the sealing effects of these two optimized packers were probed based on the finite element analysis (FEA), and the ranges of temperature and initial setting pressure for best sealing were determined. This study can provide some ideas for the material selection and structural optimization for sealing packers, aiming to ensure the safe operation of the packers in severe environments.
... Identity tensor To tackle the formidable challenge of soft actuator design, some researchers have looked to nature for inspiration in developing biomimetic designs of soft robotic arms [4]. This meta-level approach led to numerous prototypes mimicking the structure and mechanical principles of slender biological actuators such as the elephant trunk [5][6][7][8], or the octopus arm [9][10][11][12][13][14]. However, these biomimetic designs are largely based on qualitative decisions when translating the features of their biological counterparts into their respective engineering solutions. ...
The design of versatile soft actuators remains a challenging task, as it is a complex trade-off between robotic adaptability and structural complexity. Recently, researchers have used statistical and physical models to simulate the mechanical behavior of soft actuators. These simulations can help identify optimal actuator designs that fulfill specific robotic objectives. However, automated optimization of soft robots is a delicate balance between simplifying assumptions that reduce predictive fidelity and expensive simulations that limit design space exploration. Here we propose a generalized Bayesian optimization method to identify the designs of fiber-based biomimetic soft-robotic arms that minimize the actuation energy under arbitrary robotic control requirements. We use the reduced-order active filament theory as the overarching design paradigm and mechanical model, which enables a computationally robust and efficient optimization process. We evaluate the performance of our Bayesian optimization for a simple control objective in which the actuator has to reach a given target position. We show that our proposed optimization scheme outperforms a random-search baseline; it identifies more desirable designs faster and more frequently. Although we illustrate the performance of our approach for a single actuation problem, the derived method easily generalizes to the design optimization of fiber-based actuators under a large family of robotic applications.
... However, when it comes to application scenarios with complex environmental conditions (i.e., fluid fields), existing studies are limited (Li et al., 2017;Shen et al., 2017;Wu et al., 2021). To explain how combustion-enabled underwater vehicles (CUVs) interact with environmental fields, here, we report a type of underwater vehicles driven by combustion-enabled soft actuators, which can perform stable high-speed motions under dynamic fluid conditions. ...
Underwater vehicles have opened a unique path to multifunctionality and environmental adaptability. However, inadequate studies have been conducted to investigate the dynamic principle and performance of underwater vehicles in real applications with complex external conditions. Here, we propose a type of combustion‐enabled underwater vehicles that can perform stable high‐speed motions under dynamic fluid environment. Experiments are conducted to test the kinematic performance. Numerical simulations are developed to investigate the fluid–solid interaction phenomenon, and theoretical modeling is derived to study the dynamic principle of the combustion actuation process. The experimental, numerical, and theoretical results are compared with satisfactory agreements. The underwater vehicles perform ~3.4 body‐length distance within 0.2 s and a maximum speed of ~30 body‐length per second in horizontal direction. Parametric studies are conducted to investigate the sensitivity of the key factors to the kinematic performance of the reported underwater vehicles. In the end, we report the hybrid combustion‐enabled underwater vehicles (CUVs) that combined with propeller to realize continuous driving for multi‐mode operations. The experimental, numerical, and theoretical results indicate that hybrid CUVs can achieve more flexible and controllable motion performance.
... In recent researches, various soft bionic robots have been developed [8][9][10][11][12][13]. These soft bionic robots can imitate the behavior of animals in the environment. ...
This paper presents a study on the design and modeling of a novel pneumatic self-repairing soft actuator. The self-repairing soft actuator is composed of driving element, heating element, and repairing element. The driving element completes the deformation of the self-repairing soft actuator. The heating element and the repairing element complete the self-repairing function of the self-repairing soft actuator. A model used to optimize the structure is established, and the structure of the self-repairing soft actuator is determined through finite element analysis and experiment. The self-repairing time model of the soft actuator is established. The influences of different factors on the self-repairing effect and the self-repairing time are analyzed. The self-repairing scheme of the soft actuator is determined. Experiments show that the shortest time for the self-repairing soft actuator to complete the self-repairing process is 83 min. When the self-repairing soft actuator works normally, the bending angle can reach 129.8° and the bending force can reach 24.96 N. After repairing, the bending angle can reach 108.2°, and the bending force can reach 21.85 N. The repaired soft actuator can complete normal locomotion.
... Interest in soft robots, specifically soft continuum arms (SCAs), comes from their potential ability to perform complex tasks in unstructured environments as well as to operate safely around humans, with applications ranging from agriculture [1-3] to surgery [4][5][6]. An important bioinspiration for SCAs is provided by octopus arms [7][8][9][10]. An octopus arm is hyper-flexible with nearly infinite degrees of freedom, seamlessly coordinated to generate a rich orchestra of motions such as reaching, grasping, fetching, crawling or swimming [11,12]. ...
Flexible octopus arms exhibit an exceptional ability to coordinate large numbers of degrees of freedom and perform complex manipulation tasks. As a consequence, these systems continue to attract the attention of biologists and roboticists alike. In this article, we develop a three-dimensional model of a soft octopus arm, equipped with biomechanically realistic muscle actuation. Internal forces and couples exerted by all major muscle groups are considered. An energy-shaping control method is described to coordinate muscle activity so as to grasp and reach in three-dimensional space. Key contributions of this article are as follows: (i) modelling of major muscle groups to elicit three-dimensional movements; (ii) a mathematical formulation for muscle activations based on a stored energy function; and (iii) a computationally efficient procedure to design task-specific equilibrium configurations, obtained by solving an optimization problem in the Special Euclidean group SE ( 3 ) . Muscle controls are then iteratively computed based on the co-state variable arising from the solution of the optimization problem. The approach is numerically demonstrated in the physically accurate software environment Elastica . Results of numerical experiments mimicking observed octopus behaviours are reported.
... Soft miniature robots [1], ranging from nanometres to millimetres, have attracted considerable attention in recent years due to the rapid advances in material fabrication and mechanical manufacture technologies [2,3]. Soft robots have an unmatched advantage to adapt various unstructured environments with respect to their rigid counterparts, demonstrating unprecedented unique applications prospects [4][5][6], such as precise surgery [7], targeted examination [8], under-water explorations [9] and drug delivery [10]. Moreover, soft robots can exhibit safe interaction performances with human body and great flexibility to respond because of their high compliance and adaptability [11]. ...
Soft magnetic robots have attracted tremendous interest owning to their controllability and manoeuvrability, demonstrating great prospects in a number of industrial areas. However, further explorations on the locomotion and corresponding deformation of magnetic robots with complex configurations are still challenging. In the present study, we analyse a series of soft magnetic robots with various geometric shapes under the action of the magnetic field. First, we prepared the matrix material for the robot, that is, the mixture of silicone and magnetic particles. Next, we fabricated a triangular robot whose locomotion speed and warping speed are approximately 1.5 and 9 mm/s, respectively. We then surveyed the generalised types of robots with other shapes, where the movement, grabbing, closure and flipping behaviours were fully demonstrated. The experiments show that the arching speed and grabbing speed of the cross-shaped robot are around 4.8 and 3.5 mm/s, the crawling speed of the pentagram-shaped robot is 3.5 mm/s, the pentahedron-shaped robot can finish its closure motion in 1 s and the arch-shaped robot can flip forward and backward in 0.5 s. The numerical simulation based on the finite element method has been compared with the experimental results, and they are in excellent agreement. The results are beneficial to engineer soft robots under the multi-fields, which can broaden the eyes on inventing intellectual devices and equipment.
... This limits their firmness in grappling objects during underwater exploration. In recent times, there is a growing interest in the design of bionic octopus robots [12]- [14]. ...
Many modern roboticists, particularly those who model themselves after the octopus, draw inspiration from biology to construct unique robotic structures. This research expands this trend by using a biomimetic technique to create soft robots that imitate the complicated motion patterns of octopus tentacles. This method of propulsion is studied using a dynamic model of a robot with four articulated arms. This project consists of modeling, fabricating, and building an autonomous octopus robot to perform underwater investigation tasks with the aid of inspiring its movement from the octopus. The experimental results show that the adopted principle for the design works appropriately and is suitable for underwater exploration and tactical surveillance.
... Interest in soft robots, specifically soft continuum arms (SCA), comes from their potential ability to perform complex tasks in unstructured environments as well as to operate safely around humans, with applications ranging from agriculture [1][2][3] to surgery [4][5][6]. An important bio-inspiration for SCAs is provided by octopus arms [7][8][9][10]. An octopus arm is hyper-flexible with nearly infinite degrees of freedom, seamlessly coordinated to generate a rich orchestra of motions such as reaching, grasping, fetching, crawling, or swimming [11,12]. ...
Flexible octopus arms exhibit an exceptional ability to coordinate large numbers of degrees of freedom and perform complex manipulation tasks. As a consequence, these systems continue to attract the attention of biologists and roboticists alike. In this paper, we develop a three-dimensional model of a soft octopus arm, equipped with biomechanically realistic muscle actuation. Internal forces and couples exerted by all major muscle groups are considered. An energy shaping control method is described to coordinate muscle activity so as to grasp and reach in 3D space. Key contributions of this paper are: (i) modeling of major muscle groups to elicit three-dimensional movements; (ii) a mathematical formulation for muscle activations based on a stored energy function; and (iii) a computationally efficient procedure to design task-specific equilibrium configurations, obtained by solving an optimization problem in the Special Euclidean group SE(3). Muscle controls are then iteratively computed based on the co-state variable arising from the solution of the optimization problem. The approach is numerically demonstrated in the physically accurate software environment Elastica. Results of numerical experiments mimicking observed octopus behaviors are reported.
... m/s with a leg length of 0.84 m, also on 5 • slopes without additional controller actions) [190]. An underwater bipedal walking soft robot based on a coconut octopus was designed and a machine vision algorithm was used to extract motion information for analysis-such a walking robot can achieve an average speed of 6.48 cm/s [191]. The bipedal walking robot has also become a test case for the use of shape memory alloy (SMA) springs as artificial leg muscles [192]. ...
Currently, there is an intensive development of bipedal walking robots. The most known solutions are based on the use of the principles of human gait created in nature during evolution. Modernbipedal robots are also based on the locomotion manners of birds. This review presents the current state of the art of bipedal walking robots based on natural bipedal movements (human and bird) as well as on innovative synthetic solutions. Firstly, an overview of the scientific analysis of human gait is provided as a basis for the design of bipedal robots. The full human gait cycle that consists of two main phases is analysed and the attention is paid to the problem of balance and stability, especially in the single support phase when the bipedal movement is unstable. The influences of passive or active gait on energy demand are also discussed. Most studies are explored based on the zero moment. Furthermore, a review of the knowledge on the specific locomotor characteristics of birds, whose kinematics are derived from dinosaurs and provide them with both walking and running abilities, is presented. Secondly, many types of bipedal robot solutions are reviewed, which include nature-inspired robots (human-like and birdlike robots) and innovative robots using new heuristic, synthetic ideas for locomotion. Totally 45 robotic solutions are gathered by thebibliographic search method. Atlas was mentioned as one of the most perfect human-like robots, while the birdlike robot cases were Cassie and Digit. Innovative robots are presented, such asslider robot without knees, robots with rotating feet (3 and 4 degrees of freedom), and the hybrid robot Leo, which can walk on surfaces and fly. In particular, the paper describes in detail the robots' propulsion systems (electric, hydraulic), the structure of the lower limb (serial, parallel, mixed mechanisms), the types and structures of control and sensor systems, and the energy efficiency of the robots. Terrain roughness recognition systems using different sensor systems based on light detection and ranging or multiple cameras are introduced. A comparison of performance, control Citation: Mikolajczyk, T.; Mikołajewska, E.; Al-Shuka, H.F.N.; Malinowski, T.; Kłodowski, A.; Pimenov, D.Y.; Paczkowski, T.; Hu, F.; Giasin, K.; Mikołajewski, D.; et al. Recent Advances in Bipedal Walking Robots: Review of Gait, Drive, Sensors and Control Systems. Sensors 2022, 22, 4440. https:// Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/license s/by/4.0/). Sensors 2022, 22, 4440 2 of 32 and sensor systems, drive systems, and achievements of known human-like and birdlike robots is provided. Thirdly, for the first time, the review comments on the future of bipedal robots in relation to the concepts of conventional (natural bipedal) and synthetic unconventional gait. We critically assess and compare prospective directions for further research that involve the development of navigation systems, artificial intelligence, collaboration with humans, areas for the development of bipedal robot applications in everyday life, therapy, and industry.
... In addition, many researchers have also made solid progress on the design, fabrication, and control of bio-inspired aquatic robotics. As a matter of fact, since the birth of the "Robo-Tuna" by Triantafyllou et al. [19], over the last 30 years, we have witnessed a significant number of bionic swimming robots of different shapes and sizes, and the creature they mimic varies from fish (listed in detail in the following article) to all kinds of aquatic organisms, such as frogs [20,21], octopuses [22][23][24], jellyfish [25,26], etc. Their performance and the techniques involving various disciplines are aligned with continuous progress and innovation in material science, fluid mechanics, and control theory. ...
Compared with traditional underwater vehicles, bio-inspired fish robots have the advantages of high efficiency, high maneuverability, low noise, and minor fluid disturbance. Therefore, they have gained an increasing research interest, which has led to a great deal of remarkable progress theoretically and practically in recent years. In this review, we first highlight our enhanced scientific understanding of bio-inspired propulsion and sensing underwater and then present the research progress and performance characteristics of different bio-inspired robot fish, classified by the propulsion method. Like the natural fish species they imitate, different types of bionic fish have different morphological structures and distinctive hydrodynamic properties. In addition, we select two pioneering directions about soft robotic control and multi-phase robotics. The hybrid dynamic control of soft robotic systems combines the accuracy of model-based control and the efficiency of model-free control, and is considered the proper way to optimize the classical control model with the intersection of multiple machine learning algorithms. Multi-phase robots provide a broader scope of application compared to ordinary bionic robot fish, with the ability of operating in air or on land outside the fluid. By introducing recent progress in related fields, we summarize the advantages and challenges of soft robotic control and multi-phase robotics, guiding the further development of bionic aquatic robots.
... The bipedal walking process is shown in Figure 11. RU means lifting the right leg, RD means putting down the right leg, LU means lifting the left leg, LD means putting down the left leg, SS means single support, and DS means double support (Wu et al., 2021). ...
The soft organisms in nature have always been a source of inspiration for the design of soft arms and this paper draws inspiration from the octopus’s tentacle, aiming at a soft robot for moving flexibly in three-dimensional space. In the paper, combined with the characteristics of an octopus’s tentacle, a cable-driven soft arm is designed and fabricated, which can motion flexibly in three-dimensional space. Based on the TensorFlow framework, a data-driven model is established, and the data-driven model is trained using deep reinforcement learning strategy to realize posture control of a single soft arm. Finally, two trained soft arms are assembled into an octopus-inspired biped walking robot, which can go forward and turn around. Experimental analysis shows that the robot can achieve an average speed of 7.78 cm/s, and the maximum instantaneous speed can reach 12.8 cm/s.
Recent research on mobile robots has focused on increasing their adaptability to unpredictable and unstructured environments using soft materials and structures. However, the determination of key design parameters and control over these compliant robots are predominantly iterated through experiments, lacking a solid theoretical foundation. To improve their efficiency, this paper aims to provide mathematics modeling over two locomotion, crawling and swimming. Specifically, a dynamic model is first devised to reveal the influence of the contact surfaces’ frictional coefficients on displacements in different motion phases. Besides, a swimming kinematics model is provided using coordinate transformation, based on which, we further develop an algorithm that systematically plans human-like swimming gaits, with maximum thrust obtained. The proposed algorithm is highly generalizable and has the potential to be applied in other soft robots with similar multiple joints. Simulation experiments have been conducted to illustrate the effectiveness of the proposed modeling.
Sustainable development is increasingly driving the trend toward the application of biomimicry as a strategy to generate environmentally friendly solutions in the design of industrial products. Nature-inspired design can contribute to the achievement of the Sustainable Development Goals by improving efficiency and minimizing the environmental impact of each design. This research conducted an analysis of available biomimetic knowledge, highlighting the most applied tools and methodologies in each industrial sector. The primary objective was to identify sectors that have experienced greater adoption of biomimicry and those where its application is still in its early stages. Additionally, by applying the available procedures and tools to a selected case study (technologies in marine environments), the advantages and challenges of the methodologies and procedures were determined, along with potential gaps and future research directions necessary for widespread implementation of biomimetics in the industry. These results provide a comprehensive approach to biomimicry applied to more sustainable practices in product design and development.
The octopus has attracted widespread attention owing to its unique underwater movement and its ability to escape with inkjets, which also promoted the development of underwater bionic robots. This study introduces a magnetic octopus robot (MOR) 3D printed with PA6/NdFeB composite material, which has good magnetic responsiveness and rigidity to cope with complex environments. The MOR can roll and rotate through complex terrain and passages because of its eight-claw structure. It also has amphibious locomotion and can pass through narrow gaps of 37.5% of its height by deformation. In addition, the MOR can not only clamp, transport, and release solids but also liquids by adding silicone hollow spheres, which indicates the potential of the MOR to be used in medical applications for transporting solid or liquid drugs. This research will help broaden the application prospects of magnetron robots in the field of medical drug transportation.
This study proposes a novel hybrid underwater robot platform, HERO-BLUE, that integrates swimming and legged motions. HERO-BLUE is equipped with a multimodal fin comprising numerous passive joints that can act as both a swimming fin and a walking limb. This multimodal fin is integrated with a salamander-like spine and soft undulating fin in a single robot system to enable three representative locomotion modes: swimming, walking, and crawling. This paper provides details of the hardware configuration of HERO-BLUE, mathematical models for each locomotion mode, motion planning methodology, and control strategies for enabling hybrid motions. For legged motions, a dynamic simulation study was conducted to analyze the ground reaction force. The results verified the effectiveness of the proposed multimodal fin. In water tank experiments, the swimming capability was validated through thrust tests and swimming trials, and the legged motion capability was quantitatively validated in three environments, including gravel, water flow, and slopes. Furthermore, field trials were conducted in real-life scenarios in open seas, lakes, and stream beds. The experimental results show that HERO-BLUE can successively combine swimming and legged motion capability and increase underwater mobility in various challenging underwater environments.
The ocean environment has enormous uncertainty due to the influence of complex waves and undercurrents. The human beings are limited in their abilities to detect and utilize marine resources without powerful tools. Soft robots employ soft materials to simplify the complex mechanical structures in rigid robots and adapt their morphology to the environment, making them suitable for performing some challenging tasks in place of manual labor. Due to superior flexible and deformable bodies, underwater soft robots have played significant roles in numerous applications in recent decades. Meanwhile, various technical challenges still need to be tackled to ensure the reliability and practical performance of underwater soft robots in complicated ocean environment. Nowadays, some researchers have developed underwater soft robotic systems based on biomimetics and other disciplines, aiming at comprehensive exploration of ocean and appropriate utilization of unexploited resources. This review presents the recent advances of underwater soft robots in the aspects of intelligent soft materials, fabrication, actuation, locomotion patterns, power storage, sensing, control, and modeling; additionally, the existing challenges and perspectives are analyzed as well.
With the development of camera technology, high-speed cameras have greatly contributed to capturing the movement and posture of animals, which has dramatically promoted experimental biology research. At the same time, with the concept of bionics gradually gaining popularity among researchers, the design of robots is absorbing more and more biological features, where the interest in the bio-inspired robot is hewed out. Compared with the traditional robot, the bio-inspired robot imitates the motion pattern to achieve similar propulsion features, which may be more effective and reasonable. In this paper, the motion patterns of aquatic animals are divided into four categories according to their propulsion mechanisms: drag-based, lift-based, jet-based, and interface-based. And bio-inspired robots imitating aquatic prototypes are introduced and reviewed. Finally, the prospect of aquatic bio-inspired robots is discussed.
Inspired by the unique neurophysiology of the octopus, a hierarchical framework is proposed that simplifies the coordination of multiple soft arms by decomposing control into high-level decision-making, low-level motor activation, and local reflexive behaviors via sensory feedback. When evaluated in the illustrative problem of a model octopus foraging for food, this hierarchical decomposition results in significant improvements relative to end-to-end methods. Performance is achieved through a mixed-modes approach, whereby qualitatively different tasks are addressed via complementary control schemes. Herein, model-free reinforcement learning is employed for high-level decision-making, while model-based energy shaping takes care of arm-level motor execution. To render the pairing computationally tenable, a novel neural network energy shaping (NN-ES) controller is developed, achieving accurate motions with time-to-solutions 200 times faster than previous attempts. The hierarchical framework is then successfully deployed in increasingly challenging foraging scenarios, including an arena littered with obstacles in 3D space, demonstrating the viability of the approach.
Deep learning-based methods have achieved remarkable performance for single image dehazing. However, previous studies are mostly focused on the dehazing of human-perspective images without considering the practical application in the field of computer vision. Whether the image dehazing of deep learning-based methods(IDDL) can be applied in the field of computer vision will determine the research direction of computer vision dehazing scenes. This work presents a comprehensive study that the feasibility and reliability of applying IDDL from human vision to practical computer vision scenarios. An approach for practical utility and portability evaluation of the IDDL based on human vision, including the comparison regarding the detection accuracy, model running time, and model scale of the detection method, is proposed. Our research focuses on re-evaluating the applicability of image dehazing algorithms based on a computer vision perspective, including evaluation method and evaluation index. To better verify the detection effect of the dehazing algorithm, we use the synthetic dataset method as a control experiment and make a comparison with 6 state-of-the-art dehazing methods on a real-world hazy scene. Additionally, investigate the proportion of synthetic hazy images in the training dataset used, including object detection and semantic segmentation algorithms. Extensive experiments demonstrate that the poor practical utility and portability of IDDL in computer vision are verifiable, and the IDDL solution should be extensively paid attention to concerning the computer vision domain rather than leveraging the IDDL based on human vision. Finally, We provide some methods to solve the hazy scene.
The paper focuses on a preliminary study of an easy-to-customize capacitive soft sensor to measure forces that can enable soft robot features like sensitive skins or permits dexterous object manipulation thanks to the perception of the grasping force. The prototype has been realized overlapping five different layers choose among commercial and easy to find materials. The sensor is completely composed by customized or self-produced parts. The stack definition involves compatibility test to define the correct combination of layers and adhesives. An evaluation of the behavior has been performed applying weights in the range [20–5800] g finding a mean sensitivity of 0.143 pF/kg over an initial value C0 of 3.151 pF. The sensor prototype showed good performance in term of sensitivity and hysteresis in the defined application range. Dielectric viscoelastic phenomena and decreasing repeatability have been observed in the upper part of the measuring range. The sensor proposed shows promising characteristics encouraging future developments.KeywordsCapacitive force sensorConductive inksCustomizable force sensor
Aiming at the difficulty of communication and positioning of the existing underwater robot system, this article combines the vision system with a closed leader–follower formation structure to realize the underwater formation of three underwater robots. On account of the long-standing tracking requirements during vision-based formation process, an antiloss and redetecting strategy is fused in the proposed detecting and tracking algorithm and the binocular vision system can achieve real-time positioning underwater and calculate the 3-D coordinate so as to complete the follower's follow-up to the leader. An artificial submarine detection experiment and an antiloss redetection experiment are applied to demonstrate the robustness of the algorithm. And the underwater formation experiment is implemented so that the effectiveness of the proposed vision-based formation strategy is proved, which also provides a new solution for expanded formation system and multilevel cooperation.
In robotics, bioinspiration brings scenarios where soft robots acquire life-like abilities and better integrate themselves into the natural world. Because of their visual and functional similarity to biological organisms, soft robots are commonly presumed to be more “natural” and therefore more appealing than traditional rigid robots. The bio-inspired soft bending actuators play a crucial role in soft robotics and have been extensively investigated at present. The existing bending actuators are mainly achieved by the bladder’s asymmetric deformation, such as pneumatic network (Pneu-Nets) bending actuators, fiber reinforcement actuators, and braid sleeve actuators. To improve the bending efficiency and strength, a bio-inspired dual-mode actuator (DMA) with a build-in angle sensor was proposed. It couples asymmetric deformation and tendon-driven through a novel fiber winding method. A soft resistive sensor was designed and prepared for easy deployment. We then fabricate three types of bending actuators and experimentally validate the bending efficiency of the DMAs. A theoretical model for the relationship between actuation pressure and bending angle is established. To evaluate its performance, the curvature, bending angle, output force, and the bending angle of the sensor feedback were measured. The results show that DMA has good bending efficiency and output force, and the tendon has an obvious reinforcing effect on the actuator. In addition, the embedded sensor has excellent embeddable deployment performance and compatibility. Finally, demonstrates the grabbing and holding of various objects using grippers composed of different lengths and numbers of DMAs. And showed the underwater flexible manipulator operation with the three-finger gripper with bending feedback as it can estimate the size of the objected like human hand.
Here, we present ultragentle soft robotic actuators capable of grasping delicate specimens of gelatinous marine life. Although state-of-the-art soft robotic manipulators have demonstrated gentle gripping of brittle animals (e.g., corals) and echinoderms (e.g., sea cucumbers) in the deep sea, they are unable to nondestructively grasp more fragile soft-bodied organisms, such as jellyfish. Through an exploration of design parameters and laboratory testing of individual actuators, we confirmed that our nanofiber-reinforced soft actuators apply sufficiently low contact pressure to ensure minimal harm to typical jellyfish species. We then built a gripping device using several actuators and evaluated its underwater grasping performance in the laboratory. By assessing the gripper’s region of acquisition and robustness to external forces, we gained insight into the necessary precision and speed with which grasping maneuvers must be performed to achieve successful collection of samples. Last, we demonstrated successful manipulation of three live jellyfish species in an aquarium setting using a hand-held prototype gripper. Overall, our ultragentle gripper demonstrates an improvement in gentle sample collection compared with existing deep-sea sampling devices. Extensions of this technology may improve a variety of in situ characterization techniques used to study the ecological and genetic features of deep-sea organisms.
Despite the emergence of many soft-bodied robotic systems, model-based feedback control has remained an open challenge. This is largely due to the intrinsic difficulties in designing controllers for systems with infinite dimensions. In this paper we propose an alternative formulation of the soft robot dynamics which connects the robot’s behavior with the one of a rigid bodied robot with elasticity in the joints. The matching between the two system is exact under the common hypothesis of Piecewise Constant Curvature. Based on this connection we introduce two control architectures, with the aim of achieving accurate curvature control and Cartesian regulation of the robot’s impedance, respectively. The curvature controller accounts for the natural softness of the system, while the Cartesian controller adapts the impedance of the end effector for interactions with an unstructured environment. This work proposes the first closed loop dynamic controller for a continuous soft robot. The controllers are validated and evaluated on a physical soft robot capable of planar manipulation.
With the rise of soft robotics technology and applications, there have been increasing interests in the development of controllers appropriate for their particular design. Being fundamentally different from traditional rigid robots, there is still not a unified framework for the design, analysis, and control of these high-dimensional robots. This review article attempts to provide an insight into various controllers developed for continuum/soft robots as a guideline for future applications in the soft robotics field. A comprehensive assessment of various control strategies and an insight into the future areas of research in this field are presented.
Soft robotics and its related technologies enable robot abilities in several robotics domains including, but not exclusively related to, manipulation, manufacturing, human–robot interaction and locomotion. Although field applications have emerged for soft manipulation and human–robot interaction, mobile soft robots appear to remain in the research stage, involving the somehow conflictual goals of having a deformable body and exerting forces on the environment to achieve locomotion. This paper aims to provide a reference guide for researchers approaching mobile soft robotics, to describe the underlying principles of soft robot locomotion with its pros and cons, and to envisage applications and further developments for mobile soft robotics.
Swing-leg retraction in walking is the slowing or reversal of the forward rotation of the swing leg at the end of the swing phase prior to ground contact. For retraction, a hip torque is often applied to the swing leg at about the same time as stance-leg push-off. Due to mechanical coupling, the push-off force affects leg swing, and hip torque affects the stance-leg extension. This coupling makes the energetic costs of retraction and push-off depend on their relative timing. Here, we find the energy-optimal relative timing of these actions. We first use a simplified walking model with non-regenerative actuators, a work-based energetic-cost, and impulsive actuations. Depending on whether the late-swing hip torque is retracting or extending (pushing the leg forward), we find that the optimum is obtained by applying the impulsive hip torque either following or prior to the impulsive push-off force, respectively. These trends extend to other bipedal models and to aperiodic gaits, and are independent of step lengths and walking speeds. In one simulation, the cost of a walking step is increased by 17.6% if retraction torque comes before push-off. To consider non-impulsive actuation and the cost of force production, we add a force-squared (
F
2
) term to the work cost. We show that this cost promotes simultaneous push-off force and retracting torque, but does not change the result that any extending torque should come prior to push-off. A high-fidelity optimization of the Cornell Ranger robot is consistent with the swing-retraction trends from the models above.
This paper introduces the design and modelling of an underwater robot, mimicking the prototype of Antedon Petasus (Feather sea star). The design includes springs and cables driven by servomotors for the tension control of springs. In underwater environment, soft skeleton mechanisms are needed for the proper interaction. This can be achieved by using soft robotic links like cable driven springs using servomotors in various propulsion patterns. The cable-driven structure is a kind of parallel mechanism transmitting forces and motions by cables which are connected to the motors mounted on a fixed base. Solidworks is used to model it. The software, Ansys Fluent is used for its analysis in underwater environment and for the estimation of drag co-efficient.
This paper studies underwater legged locomotion (ULL) by means of a robotic octopus-inspired prototype and its associated model. Two different types of propulsive actions are embedded into the robot model: reaction forces due to leg contact with the ground and hydrodynamic forces such as the drag arising from the sculling motion of the legs. Dynamic parameters of the model are estimated by means of evolutionary techniques and subsequently the model is exploited to highlight some distinctive features of ULL. Specifically, the separation between the center of buoyancy (CoB)/center of mass and density affect the stability and speed of the robot, whereas the sculling movements contribute to propelling the robot even when its legs are detached from the ground. The relevance of these effects is demonstrated through robotic experiments and model simulations; moreover, by slightly changing the position of the CoB in the presence of the same feed-forward activation, a number of different behaviors (i.e. forward and backward locomotion at different speeds) are achieved.
The octopus is an interesting model for the development of soft robotics, for its high deformability, dexterity and rich behavioural repertoire. To investigate the principles of octopus dexterity, we designed an eight-arm soft robot and evaluated its performances with focused experiments. The OCTOPUS robot presented here is a completely soft robot, which integrates eight arms extending in radial direction and a central body which contains the main processing units. The front arms are mainly used for elongation and grasping, while the others are mainly used for locomotion. The robotic octopus works in water and its buoyancy is close to neutral. The experimental results show that the octopus-inspired robot can walk in water using the same strategy as the animal model, with good performance over different surfaces, including walking through physical constraints. It can grasp objects of different size and shape, thanks to its soft arm materials and conical shape.
In this paper a model is presented which describes an octopus-inspired robot capable of two kinds of locomotion: crawling and bipedal walking. Focus will be placed on the latter type of locomotion to demonstrate, through model simulations and experimental trials, that the robot’s speed increases by about 3 times compared to crawling. This finding is coherent with the performances of the biological counterpart when adopting this gait. Specific features of underwater legged locomotion are then derived from the model, which prompt the possibility of controlling locomotion by using simple control and by exploiting slight morphological adaptations.
Remotely operated crawlers are specialized vehicles that allow for underwater intervention by staying in direct contact with the seafloor. The crawler offers a very stable platform for manipulating objects or for taking measurements. Additionally, crawlers lend themselves to long-term work. Crawlers are already well established platforms for various environments. For example, planetary rovers have successfully proven themselves in missions to the moon and mars. At Florida Institute of Technology a hybrid remotely operated crawler has been developed for archaeological and scientific activities within coastal regions of the ocean. This hybrid vehicle combines a standard 40-cm high, 53-cm wide, 71-cm long remotely operated vehicle (ROV) flyer with a 1.0-m high, 1.52-m wide, 2.8-m long remotely operated vehicle crawler for multiple research activities such as underwater archaeology documentation and artifact removal. Named the RG-III, the hybrid vehicle is currently designed to operate in depths down to 100-m. The vehicle is controlled by a remote control cable from the beach or boat and is equipped with video, still cameras and robotic grippers. Capable of carrying most environmental data gathering instruments the crawler is also able to "fly" when necessary by filling flotation bladders and using its four mounted thrusters. This capability allows the vehicle to jump from one side of a shipwreck to another or to fly over sensitive regions such as reefs. The ROV-flyer piggy-backs on the ROV-crawler and can separate to become an "eye-in-the-sky" to observe from above the activities of the ROV-crawler.
The design concept and development of a multi-
purpose, underwater robot is presented. The final robot consists
of a continuum composed for 80% of its volume of rubber-
like materials and it combines locomotion (i.e. crawling and
swimming) and manipulation capabilities. A first prototype of the
robot is illustrated based on the integration of existing prototypes.
Here we report bipedal movement with a hydrostatic skeleton. Two species of octopus walk on two alternating arms using a rolling
gait and appear to use the remaining six arms for camouflage. Octopus marginatus resembles a coconut, and Octopus (Abdopus) aculeatus, a clump of floating algae. Using underwater video, we analyzed the kinematics of their strides. Each arm was on the sand
for more than half of the stride, qualifying this behavior as a form of walking.
We have developed a biomimetic robot based on the American lobster. The robot is designed to achieve the performance advantages of the animal model by adopting biomechanical features and neurobiological control principles. Three types of controllers are described. The first is a state machine based on the connectivity and dynamics of the lobster central pattern generator (CPG). The state machine controls myomorphic actuators based on shape memory alloys (SMAs) and responds to environmental perturbation through sensors that employ a labelled-line code. The controller supports a library of action patterns and exteroceptive reflexes to mediate tactile navigation, obstacle negotiation and adaptation to surge. We are extending this controller to neuronal network-based models. A second type of leg CPG is based on synaptic networks of electronic neurons and has been adapted to control the SMA actuated leg. A brain is being developed using layered reflexes based on discrete time map-based neurons.
Fish’s outstanding motion and coordination performance make it an excellent source of inspiration for scientists and engineers aiming to design and control next-generation autonomous underwater vehicles within the framework of bionics. This paper offers a general review of the current status of bionic robotic fish, with particular emphasis on the hydrodynamic modeling and testing, kinematic modeling and control, learning and optimization, as well as motion coordination control. Among these aspects, representative studies based on ideas and concepts inspired from fish motion and coordination are discussed. At last, the major challenges and the future research directions are addressed in the context of integration of various research streams from ichthyologic, hydrodynamic, mechanical, electronic, control, and artificial intelligence. Further development of bionic robotic fish can be utilized to execute some specific missions in complex underwater environments, where operations are unsafe or impractical for divers or conventional underwater vehicles.
We report on the model-based development of the pronking and trotting behaviors of a leg-wheel transformable robot. The spring-loaded inverted pendulum (SLIP) model serves as the motion template; its stable running motion is investigated, and the parameters and state conditions suitable for implementation in the robot are selected. Mapping between the SLIP model and the robot is conducted so that the running of the SLIP model can be transformed into the robot’s pronking and trotting behaviors. The spring effect of the leg-wheel is achieved using force control with motor current feedback. The robot was operated to initiate four different dynamic behaviors with variations in stiffness and gait based on four different fixed-point trajectories of the SLIP model. The experimental results confirm that the proposed strategy is effective in initiating the dynamic behaviors.
The sand-dwelling octopus Macrotritopus defilippi was filmed or photographed in five Caribbean locations mimicking the swimming behavior (posture, style, speed, duration) and coloration of the common, sand-dwelling flounder Bothus lunatus. Each species was exceptionally well camouflaged when stationary, and details of camouflaging techniques are described for M. defilippi. Octopuses implemented flounder mimicry only during swimming, when their movement would give away camouflage in this open sandy habitat. Thus, both camouflage and fish mimicry were used by the octopuses as a primary defense against visual predators. This is the first documentation of flounder mimicry by an Atlantic octopus, and only the fourth convincing case of mimicry for cephalopods, a taxon renowned for its polyphenism that is implemented mainly by neurally controlled skin patterning, but also—as shown here—by their soft flexible bodies.
This chapter reports on the conceptual design of an octopus-inspired robot. The investigation started from slow speed gaits, such as the crawling locomotion of octopuses, and was followed by faster gaits such as bipedal walking and hopping. Results envisage that this novel locomotion can be exploited to increase the mobility of underwater robots in the benthic realm.
In this letter, a fundamental model for underwater legged locomotion, called U-SLIP, is presented and implemented on a robotic platform. Unlike traditional locomotion models, U-SLIP addresses specific hydrodynamic contributions, such as drag, buoyancy, and added mass. By taking as a reference the U-SLIP model, we derived the design principles to build an effective underwater legged robot able to achieve self-stabilizing running. For the first time, a robotic platform can exhibit a dynamic mode of locomotion composed of swimming and pushing phases, demonstrating self-stabilizing running with a little control. Experiments conducted over different uneven terrains corroborate the effectiveness of the proposed model.
We describe the design features that underlie the operation of iSprawl, a small (0.3 kg) autonomous, bio-inspired hexapod that runs at 15 body-lengths/second (2.3 m/s). These features include a tuned set of leg compliances for efficient running and a light and flexible power transmission system. This transmission system permits high speed rotary power to be converted to periodic thrusting and distributed to the tips of the rapidly swinging legs. The specific resistance of iSprawl is approximately constant at 1.75 for speeds between 1.25 m/s and 2.5 m/s. Examination of the trajectory of the center of mass and the ground reaction forces for iSprawl show that it achieves a stable, bouncing locomotion similar to that seen in insects and in previous (slower) bio-inspired robots, but with an unusually high stride frequency for its size.
The outstanding locomotor and manipulation characteristics of the octopus have recently inspired the development, by our group, of multi-functional robotic swimmers, featuring both manipulation and locomotion capabilities, which could be of significant engineering interest in underwater applications. During its little-studied arm-swimming behavior, as opposed to the better known jetting via the siphon, the animal appears to generate considerable propulsive thrust and rapid acceleration, predominantly employing movements of its arms. In this work, we capture the fundamental characteristics of the corresponding complex pattern of arm motion by a sculling profile, involving a fast power stroke and a slow recovery stroke. We investigate the propulsive capabilities of a multi-arm robotic system under various swimming gaits, namely patterns of arm coordination, which achieve the generation of forward, as well as backward, propulsion and turning. A lumped-element model of the robotic swimmer, which considers arm compliance and the interaction with the aquatic environment, was used to study the characteristics of these gaits, the effect of various kinematic parameters on propulsion, and the generation of complex trajectories. This investigation focuses on relatively high-stiffness arms. Experiments employing a compliant-body robotic prototype swimmer with eight compliant arms, all made of polyurethane, inside a water tank, successfully demonstrated this novel mode of underwater propulsion. Speeds of up to 0.26 body lengths per second (approximately 100 mm s(-1)), and propulsive forces of up to 3.5 N were achieved, with a non-dimensional cost of transport of 1.42 with all eight arms and of 0.9 with only two active arms. The experiments confirmed the computational results and verified the multi-arm maneuverability and simultaneous object grasping capability of such systems.
To cope with the exceptional computational complexity that is involved in the control of its hyper-redundant arms [1], the octopus has adopted unique motor control strategies in which the central brain activates rather autonomous motor programs in the elaborated peripheral nervous system of the arms [2, 3]. How octopuses coordinate their eight long and flexible arms in locomotion is still unknown. Here, we present the first detailed kinematic analysis of octopus arm coordination in crawling. The results are surprising in several respects: (1) despite its bilaterally symmetrical body, the octopus can crawl in any direction relative to its body orientation; (2) body and crawling orientation are monotonically and independently controlled; and (3) contrasting known animal locomotion, octopus crawling lacks any apparent rhythmical patterns in limb coordination, suggesting a unique non-rhythmical output of the octopus central controller. We show that this uncommon maneuverability is derived from the radial symmetry of the arms around the body and the simple pushing-by-elongation mechanism by which the arms create the crawling thrust. These two together enable a mechanism whereby the central controller chooses in a moment-to-moment fashion which arms to recruit for pushing the body in an instantaneous direction. Our findings suggest that the soft molluscan body has affected in an embodied way [4, 5] the emergence of the adaptive motor behavior of the octopus.
Copyright © 2015 Elsevier Ltd. All rights reserved.
The paper presents a vehicle with a biomimetic level pectoral fin. Firstly, muscle structure of cuttlefish's pectoral fin is analyzed, and undulatory movement of cuttlefish's pectoral fin is simplified. Meanwhile a kinematics model is built for hydromechanics theory analysis. Secondly,
a vehicle with a biomimetic level pectoral fin based on a flexible fin unit actuated by shape memory alloy (SMA) wires is designed. Finally, swimming performances is experimented. Experimental results show that the vehicle can realize undulatory swimming by the biomimetic pectoral fin. The
swimming speed and theoretical thrust increase with the heating pulse width. The maximum swimming speeds is up to 33 mm/s.
Soft robots have significant advantages over traditional rigid robots because of their morphological flexibility. However, the use of conventional engineering approaches to control soft robots is difficult, especially to achieve autonomous behaviors. With its completely soft body, the octopus has a rich behavioral repertoire, so it is frequently used as a model in building and controlling soft robots. However, the sensorimotor control strategies in some interesting behaviors of the octopus, such as octopus crawling, remain largely unknown. In this study, we review related biological studies on octopus crawling behavior and propose its sensorimotor control strategy. The proposed strategy is implemented with an echo state network on an octopus-inspired, multi-arm crawling robot. We also demonstrate the control strategy in the robot for autonomous direction and speed control. Finally, the implications of this study are discussed.
In this paper a locomotion strategy for a six-limb robot inspired by the octopus is shown. A tight relationship between the muscular system and the nervous systems exists in the octopus. At a high level of abstraction, the same relationship between the mechanical structure and the control of the robot is presented here. The control board sends up to six signals to the limbs, which mechanically perform a stereotypical rhythmical movement. The results show how by coordinating only two limbs an effective locomotion is achieved.
A simple spring-mass model consisting of a massless spring attached to a point mass describes the interdependency of mechanical parameters characterizing running and hopping of humans as a function of speed. The bouncing mechanism itself results in a confinement of the free parameter space where solutions can be found. In particular, bouncing frequency and vertical displacement are closely related. Only a few parameters, such as the vector of the specific landing velocity and the specific leg length, are sufficient to determine the point of operation of the system. There are more physiological constraints than independent parameters. As constraints limit the parameter space where hopping is possible, they must be tuned to each other in order to allow for hopping at all. Within the range of physiologically possible hopping frequencies, a human hopper selects a frequency where the largest amount of energy can be delivered and still be stored elastically. During running and hopping animals use flat angles of the landing velocity resulting in maximum contact length. In this situation ground reaction force is proportional to specific contact time and total displacement is proportional to the square of the step duration. Contact time and hopping frequency are not simply determined by the natural frequency of the spring-mass system, but are influenced largely by the vector of the landing velocity. Differences in the aerial phase or in the angle of the landing velocity result in the different kinematic and dynamic patterns observed during running and hopping. Despite these differences, the model predicts the mass specific energy fluctuations of the center of mass per distance to be similar for runners and hoppers and similar to empirical data obtained for animals of various size.
Crabster robot deployed during south Korean ferry disaster
- Hsu
A bionic jellyfish robot propelled by bio-tentacle propulsors actuated by shape memory alloy wires
- Jian
Jian L, Yanling G and Zhenlong W 2014 A bionic jellyfish
robot propelled by bio-tentacle propulsors actuated by
shape memory alloy wires J Harbin Instit. Technol. 46 104
Dynamic control of soft robots interacting with the environment
- Della Santina
- C Katzschmann
- R K Biechi
- A Rus
Della Santina C, Katzschmann R K, Biechi A and Rus D
2018 Dynamic control of soft robots interacting with the
environment 2018 IEEE Int. Conf. on Soft Robotics
(RoboSoft) (Piscataway, NJ: IEEE) 46-53
Crabster robot deployed during south Korean ferry disaster Spectrum
- J Hsu
Hsu J 2014 Crabster robot deployed during south Korean
ferry disaster Spectrum